Cutting instruments have been used for centuries by craftsmen, hunters, and others requiring a sharp cutting instrument. Pocket knives are commonly used by sportsmen, craftsmen and others who desire a compact, portable blade which can be safely folded and transported in a pocket or attached to a belt. More recently, fixed length knives have been replaced with popular folding knives, which generally have two positions: open and closed. In an open or extended position of use, the knife cutting blade is extended to expose the blade cutting edge and permit cutting. In a closed position, the cutting edge of the blade is stored within a cavity or recess in the handle portion of the knife, thus preventing the blade from being exposed. The folding knife further provides a cutting instrument which is much shorter in length, when in a closed position, than a typical fixed blade knife. Although folding knives are extremely convenient, they can potentially become dangerous if the cutting blade does not have a locking mechanism to securely keep the knife blade in the extended position of use. U.S. Pat. No. 6,751,868 discloses a folding knife with a substantially spherical locking mechanism, and is incorporated by reference herein in its entirety.
Although there are other types of locking mechanisms used to prevent the inadvertent closure of a folding knife blade, such as a liner lock, which utilizes a leaf spring positioned within the cavity of the knife handle and which engages the heel end of the knife blade, or a single piece backlock, which utilizes a locking bar positioned along an upper edge of the knife handle, many of these locking mechanisms are not simplistic to use, are expensive to manufacture, or are prone to failure. Additionally, with both liner locks and backlock locking mechanisms, it is possible for the locking apparatus to potentially become disengaged from the blade after excessive and continuous use. Thus, there is a need for a type of folding knife locking mechanism which overcomes these pitfalls and is simplistic to use, inexpensive to manufacture, and provides substantial strength to prevent any inadvertent failure. There is also a need for an improved folding knife locking mechanism that is simplistic to assemble, uses a minimum number of components, and is extremely reliable to prevent the inadvertent closure of the knife blade. There is an additional need for a lock release mechanism that allows quick and easy manipulation by a user's thumb on a side of the folding knife handle to assure quick closing.